keybase id fails to find keybased.sock on OS X

```
rb@silverbird$ keybase id rptb1

We couldn't connect but there is a Keybase service (keybase.service) running (743).

You might try restarting it: keybase launchd restart keybase.service

▶ ERROR There were multiple errors: dial unix /Volumes/Silverbird-HD/Local/Users/rb/Library/Group Containers/keybase/Library/Caches/Keybase/keybased.sock: connect: invalid argument; dial unix /Volumes/Silverbird-HD/Local/Users/rb/Library/Caches/Keybase/keybased.sock: connect: no such file or directory
```
Note, relaunching the service does not help. So I did some poking around then tried symbolic links from to the Group Containers directory from the other Caches directory, like this:
```
rb@silverbird$ pwd
/Volumes/Silverbird-HD/Local/Users/rb/Library/Caches/Keybase
rb@silverbird$ ls -l
total 32
-rw-r--r-- 1 rb staff 89 12 Sep 13:05 kbfs.info
lrwxr-xr-x 1 rb staff 104 12 Sep 13:24 kbfsd.sock -> /Volumes/Silverbird-HD/Local/Users/rb/Library/Group Containers/keybase/Library/Caches/Keybase/kbfsd.sock
-rw-r--r-- 1 rb staff 94 12 Sep 13:18 keybased.info
lrwxr-xr-x 1 rb staff 107 12 Sep 13:24 keybased.sock -> /Volumes/Silverbird-HD/Local/Users/rb/Library/Group Containers/keybase/Library/Caches/Keybase/keybased.sock
```
This allowed id to complete.
```
rb@silverbird$ keybase id rptb1
▶ INFO Identifying rptb1
✔ "rptb1" on reddit: https://www.reddit.com/r/KeybaseProofs/comments/9f10l8/my_keybase_proof_redditrptb1_keybaserptb1/
✔ "rptb1" on github: https://gist.github.com/e67c8b07c74b34cd11330f733f347a78
✔ "rptb1" on twitter: https://twitter.com/rptb1/status/1039608884128821249
✔ "richard.brooksby" on facebook: https://www.facebook.com/richard.brooksby/posts/10102993592483830
```
However, it did not help with https://github.com/keybase/client/issues/5399#issuecomment-420280044

There seems to be some directory confusion going on. Has someone assumed something about paths to home directories?

The log id *after* the symlink hack above is acb314d287d41384527ce11c

I'm running OS X 10.11.6.

Start by reproducing `keybase id rptb1` on OS X 10.11.6 with the reported relocated home-directory paths, then compare the socket locations under `Library/Caches/Keybase` and `Group Containers/keybase/Library/Caches/Keybase`. Trace the path selection used by the client and launchd service; done means `keybase id` connects without manually creating symlinks.

Written by the indexing model from the issue text.